This 16th-century monastery has been turned into a surrealist architecture compound.

This ruined fort hidden at the top of Central Park can't seem to keep from losing its historical plaques.

A state-of-the-art medical facility from the Imperial era is now a derelict ruin.

Natural time capsule containing an alien ecosystem.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

The 953 windows undoubtedly make this the world's most beautiful screened porch.

The world's first underground farm is in a World War II bomb shelter beneath the streets of London.

This elegant arc of a waterfall marks a religious turning point.

Ride the subways of yesteryear.

As can be expected from a centuries old church built in a canal city, the undercroft of this house of worship is beautifully flooded.

Surreal riveted sea forts once protected the Kent shores from German attack.

Houses are tucked between, on, and underneath giant boulders.

Japanese island famous for poison gas and fluffy bunnies.

One of the most beautiful bookstores in the world hides a neo-Gothic interior behind an art nouveau facade.

A fantastic castle rumored to be the birthplace of King Arthur.

This eye-popping Icelandic crater lake is surrounded by red volcanic rock.

This medieval castle overlooking the Elzbach river looks just like it did hundreds of years ago.

The hidden lair of an alchemist rediscovered in a 2002 flood.

Walk 2,300 feet above the ground on the "Troll's Tongue."

This eccentrically decorated palace is replete with grottoes, fountains, tunnels, and caves.

An Aztec snake god has taken the material form of an apartment complex.

An ethereal glowing blue ocean cave in Croatia.

A tunnel once abandoned now thrives with graffiti art as an off-limits makeshift gallery.

One of only two commuter aerial tramways in the United States.